This study will deal with phoneme errors associated with room reverberation, T, one of the most common distortions of speech in everyday life. In the first part, effect of reverberation on speech understanding by subjects from various age groups will be tested with Modified Rhyme Test. Three Ts, ranging between 0.5 and 1.5 s, typical for offices, auditoriums and churches will be used. Age range of subjects will be from 20 to 70-plus years. Subjects will have normal hearing or mild hearing losses. Dependence of speech understanding on age and T will be established. In the second part, phoneme confusions associated with reverberation will be investigated for subjects with various configurations of hearing loss. Range of T will be between 0.25 and 0.75 s, typical for small offices, classrooms and living quarters, common everyday listening environments of hearing-impaired listeners. Two separate tests will be constructed: 1) sentences with nonsense syllables to test identification of 16 consonants in initial and final positions, and 2) sentences with one-syllable words to test identification of 15 vowels. The pattern of errors will be established for four groups of subjects: 1) with normal hearing, 2) with mild flat losses, 3) with sloping losses, 4) with moderate to severe flat losses; for consonants in initial and final positions and for vowels at three Ts. Since a small number of vowel errors is anticipated, change in the quality of vowels (timbre) will also be investigated. Each vowel recorded at three Ts will be cut off from the test word and compared with its own non-reverberant pattern. Similarity judgments will be obtained using a seven-point scale. All tests will be recorded, processed through a reverberant field and reproduced for subjects through a loudspeaker. The study will assess speech perception difficulties in reverberation by elderly and hearing-impaired listeners. This information can be used in counselling, auditory rehabilitation, and as a guideline for developing clinical procedures including reverberation as a parameter. This parameter may improve hearing aid fitting and initial acceptance of aids by patients.